GB1284882A - Methods of producing luminescent materials - Google Patents

Abstract

1284882 Luminescent materials and uses thereof WESTERN ELECTRIC CO Inc 11 Aug 1969 [12 Aug 1968] 40025/69 Heading C4S A method of producing a luminescent material comprises evaporating a luminescent compound of fluorine and an element from Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb and a host material on a substrate so that each is uniformly dispersed and the compound substantially undissociated. The compound may be in amount 0À1 to 10 molar per cent, up to 30 and 35 mole per cent also being instanced and may be YbF 3 , NdF 3 , ErF 3 , TmF 3 , HoF 3 , TbF 3 , PrF 3 , DyF 3 , EuF 3 and EuF 2 vaporized between 900‹ to 1000‹ and 1200‹ C. and the host may be ZnS vaporized between 910‹ and 1000‹ C. (800‹ C. also instanced). The substrate may be at room temperature and the pressure 10<SP>-5</SP> to 10<SP>-5</SP> mms. Hg. Fluorides of the transition metals are instanced such as 0À1 to 0À5 mol. per cent MnF 2 vaporized at 600‹ to 900‹ C. with a ZnS host. Impurities are preferably <0À1%. The host material preferably has a high order of crystalline perfection although in thin film EL devices, polycrystalline films may be used, and powders are mentioned as cathodoluminescent and EL materials, emitting in the U.V., infra-red and visible, lamp, display panel and c.r.t.'s being specified devices. Cathodoluminescent host materials may also be zinc silicates and yttrium vanadates. The emission centre concentration for cathodoluminescence is preferably an order of magnitude higher than for electroluminescence. An EL device may include a tunnel injecting contact formed by 10 to 300 Š insulator 32 and conductor 33 with thin luminescent film 30, a Schottky junction injection contact device (Fig. 2, not shown) operated on D.C., while Fig. 3 (not shown) includes a thick blocking insulator 52 (e.g. 1000 Š to several Á) preferably A.C. operated. Host materials permitting majority carrier injection include II-VI compounds such as ZnO, ZnS, ZnTe, CdS, CdSe, CdTe, and mixed crystals such as ZnSZnSe, ZnS-ZnO, III-V compounds such as GaAs, GaP, GaN, AlN; Group IV elements and compounds such as C, SiC, Si, Ge, and Group II halide compounds such as CdF 2 . If Gd<SP>3+</SP> is used, the host is preferably CdF 2 or AlN. As EL materials, ZnS and CdF 2 are preferred for fabrication as thin films and SiC for chemical stability. Hosts amenable to vaporizing by heating include ZnO or SiC, the latter also being vaporizable by electron gun or reactive pyrrolytic techniques. If the luminescent compound is less stable in the host, the material temperature should be controlled such as below 1200‹ C., for instance a 1000 Š to 5000 Š film of TbF 3 in ZnS is maintained below 1000‹ C.